1. Field of the Invention
The present invention relates generally to griddles for cooking and specifically to griddles having microwave and convection assistance to reduce cooking times.
2. Description of Related Art
The griddle is a basic piece of equipment in a large number of commercial food service establishments. Griddle cooking, which is conduction cooking, has several very desirable effects, including coagulation of proteins, flavor development (e.g., browning of meats), tenderizing some animal tissues, fat melting (e.g., bacon), product drying (e.g., pancakes), and the development of crusts. These cooking qualities, coupled with the simple construction and operation of the griddle, have made it an indispensable cooking device in most commercial kitchens.
Modern griddles come in several configurations, including both conventional griddle and clamshell griddles. A conventional (single-sided) griddle consists of a single heated platen that is typically either electric or gas-fired. The griddle will have simple thermostat control of one or more cook zones featuring a flat or grooved griddle platen. A clamshell griddle is a flat or grooved griddle platen with an additional hinged upper platen that cooks the top side of the product.
Commercial single-sided griddles have a number of disadvantages and limitations, including 1) relatively high heat gain to the kitchen, 2) high operating costs, 3) lengthy pre-cooking warm-up time, 4) undesirable variation in batch-to-batch cooking times, 6) uneven heat transfer to the food items being cooked, and/or 7) the inability to vary the relative cooking rates for small or large food portions. With a single-sided griddle it is necessary for the operator to turn product (e.g., hamburger patties) over after they have been cooked on one side for cooking on the second side. This increases the amount of operator attention required for cooking these food products and also increases the cooking time. A typical technique employed by restaurants to insure that the food is properly cooked (food safety need) is to “flip” or turn the food product always to an adjacent hot griddle platen area thereby effectively reducing the usable service of the griddle platen.
Improved singled-sided griddle designs such as high-pressure steam heated griddles or those featuring very conductive griddle materials (e.g., copper clad with thin stainless) have greatly reduced griddle plate temperature variation and provided for faster recovery times. Having a cook surface with a more uniform temperature coupled with a fast temperature recovery increases the cook capacity of the griddle (weight of cook per area per minute). Reducing griddle surface temperature variations also achieves a decrease in food safety issues. While these improvements are desirable, they have a significantly increased fabrication cost above the costs for a conventional griddle. Two-sided griddles were developed to further improve speed, cooking capacity, and food safety.
Two-sided griddles utilizing both upper and lower cooking platens have been in use for many years. Early adopters of this technology were driven to do so by the need to shorten cook times for hamburger patties as well as to greatly reduce food safety concerns. A two-sided griddle also reduces the amount of operator attention and training required for cooking hamburger patties. A hamburger patty cook time may be reduced by 50% (2× the cooking speed) when compared to cook times on a conventional griddle. Two-sided griddle designs may be divided into three categories: 1) non-contact upper platen (“conventional two sided method”), 2) contact upper platen, and 3) broiler upper platen (“Lang method”).
A conventional, non-contact clamshell griddle has a lower griddle platen that may be heated by either electric resistance heating or by gas fueled burners. Typically, an upper platen is electrically heated, and the platen is made from aluminum or steel. The upper clamshells are typically about 2 feet wide, so that a 4-foot griddle would utilize 2 independent clamshells. The upper cooking platens are generally large enough to enable the operator to cook a number of individual hamburger patties or other items at the same time. During operation the upper platen is lowered to just above the food, which is positioned on the lower griddle platen. To maximize heat transfer to the top surface of the food product, the top platen is positioned as close as possible to the product without contacting the product. By avoiding contact, the heat transfer rate is reduced, but it eliminates the possibility of product sticking to the upper platen when it is raised at the end of the cook cycle. The upper platen is moved to an open position to allow his easy access to the lower griddle surface. A clamshell griddle can be used as conventional singled sided griddle for product not suitable for two-sided cooking (e.g., products of non-uniform cross-section).
A griddle having a contact upper platen is typically used to apply heat to both sides of a relatively thin, homogenous product, such as a hamburger patty. This type of cooking reduces the length of the conduction path to the center of the product by about 50%, and cook times are approximately halved. The contact upper platen griddle design accomplishes this goal by contacting and pressing down on the product with the upper platen during the cook cycle. One method of preventing food product from sticking to the upper platen involves using a Teflon® release sheet placed between the upper surface of the product and the cooking surface of the upper platen. This permits high heat transfer rates but eliminates the sticking of product to the cooking surface of the upper platen.
Cooking hamburger patties using this approach requires the contact-style double-sided griddle to have a number of special features, including the need for the upper platen cooking surface to remain parallel to the lower cooking surface through out the cooking process and that the upper griddle move downwards as the patty shrinks. For example, frozen patties are relatively rigid when initially placed on the lower cooking platen. If the upper platen rests only on the thickest patty or patties, even small differences in the platens being parallel form right-to-left or front-to-back or small variations in patty thickness can prevent or delay proper heat transmission from the upper platen to some of the product. This can result in non-uniform product center temperatures yielding poor product quality or causing food safety issues. On the other hand, the patties typically soften and shrink or decrease in thickness as they thaw and cook, and the weight of the upper cooking platen can excessively compress the hamburger patties, which can adversely affect the texture and appearance of the cooked patties. Therefore, control of the motion of the platen is critical for a properly cooked product.
Two-sided grills with a contact upper platen present several special problems including: 1) accommodating variations in initial thickness of the individual patties in the group being cooked; 2) accommodating the decrease in thickness of the patties that occurs during cooking; 3) preventing excessive compaction of the patties; and 4) accommodating different groups of patties of nominally different thicknesses. In addition, there is the problem of moving a relative heavy upper platen at the beginning and end of the cooking cycle. The platen weight requires the use of very robust lift mechanisms that provides for uniform contact with the food product and provides for a controlled drop as the food product shrinks. Using a release sheet to prevent food from sticking to the upper platen is both expensive and adds operational complexity. In addition, the preformed food, such as hamburger patties that come in several different nominal sizes and thicknesses and are commonly frozen, must have precise production dimensional tolerances relative to thickness if the contact approach is to work well.
Another variation of the doubled sided griddle is a griddle with a broiler clamshell in place of a clamshell upper platen. This arrangement is desirable in that the broiler subsystem cooks by radiation and does not need to be in contact with the food product to provide good top side cooking performance. Benefits include the ability to cook products of non-uniform thickness, fast recovery heat-up time for a natural-gas fueled clamshell broiler (but not with electric option due to practical power limitations), and a lighter weight clamshell assembly (heavy platens being replaced by lighter burners). However, this approach has several limitations, including: 1) longer cooking times than that provided by a contact double-sided griddle; 2) smoke issues as the oils and grease generated by the cooking process flash upon contact with hot radiant elements; 3) the inability to regulate broiler radiant temperature for different foods; 4) reduced radiant burner life due to the burners being close to the lower platen and directly exposed to cooking grease/oil contamination; and 5) a large heat gain to the kitchen.
One way to increase the speed of cooking within a microwave oven or a microwave-convection oven is to add a griddle within the oven. This is known in the art and is referred to as a grill or hot bottom. Such a feature is desirable since it provides browning of the food product, which is not otherwise achieved with microwave cooking. A griddle is used to cook food by direct contact with a metal plate maintained at an elevated temperature (e.g., 300° F. (148.89° C.) to 375° F. (190.56° C.) by applying heat to the interior or bottom side of the platen. In one such oven, the griddle is located in an aperture in the floor of the cooking cavity.
An oven with a griddle plate differs fundamentally from a double-sided griddle in several areas including:
1) A griddle has an independent, temperature-controlled lower bottom platen, whereas a hot plate or pan is slaved to the oven temperature. No independent top and bottom energy control is provided for cooking food placed on a griddle plate in oven.
2) In a clamshell griddle the upper heating means moves relative to the food placed on the lower griddle surface, whereas in an oven the entire heating means remains fixed relative to the food placed in the oven cavity.
3) A clamshell griddle can be operated as conventional one sided griddle, whereas an oven with a griddle function always applies energy to the top and bottom of the food.
4) Ovens with a griddle function control energy to the food based primarily on oven air temperature and not the actual griddle plate conditions.
Although great strides have been made in the area of griddles, many short comings remain.